1. Field of the Invention
The present invention relates to a sensor of an electromagnetic induction type coordinate input device, and more particularly to a pattern formation of loop coils formed on a substrate in the sensor of an electromagnetic induction type input device.
2. Description of the Related Art
An electromagnetic induction type coordinate input device is composed of a sensor in which a large number of loop coils are disposed in an X-axis direction and in a Y-axis direction in coordinate axes, and a position indicator having a resonance circuit consisting of a coil and a capacitor. Thus, the electromagnetic induction type coordinate input device detects coordinate values of the X-axis direction and the Y-axis direction of a position indicated by the position indicator on the basis of electromagnetic induction between the position indicator and the sensor.
FIG. 9 is a top plan view showing an example of a structure of a conductor pattern in a conventional sensor of a coordinate input device. In a sensor 100A of this example, a loop coil group 1 in the X-axis direction (for example, in a transverse direction of a substrate 3) is formed on one surface of the substrate 3, and a loop coil group 2 in the Y-axis direction (for example, in a longitudinal direction of the substrate 3) is formed on the other surface on a side opposite to the one surface of the substrate 3.
In the example shown in FIG. 9, the loop coil group 1 in the X-axis direction is composed of 12 X-axis direction loop coils 1X1 to 1X12. The X-axis direction loop coils 1X1, 1X2, . . . , 1X12 are composed of loop portions 1X1L, 1X2L, . . . , 1X12L which surround elongated rectangular areas in the Y-axis direction, respectively, and extraction line portions 1X1E, 1X2E, . . . , 1X12E which are continuously connected to the loop portions 1X1L, 1X2L, . . . , 1X12L, respectively.
Also, the 12 X-axis direction loop coils 1X1 to 1X12 are disposed in such a way that the loop portions thereof 1X1L to 1X12L are arranged in the X-axis direction, and are formed in such a way that the extraction line portions thereof 1X1E to 1X12E extend individually in the Y-axis direction from the loop portions 1X1L to 1X12L, respectively. Also, each of the extraction line portions 1X1E to 1X12E is bent at a right angle in the X-axis direction so as to be connected to a connector portion 4.
In addition, in the example shown in FIG. 9, the Y-axis direction loop coil group 2 is composed of eight Y-axis direction loop coils 2Y1 to 2Y8. The Y-axis direction loop coils 2Y1, 2Y2, . . . , 2Y8 are composed of loop portions 2Y1L, 2Y2L, . . . , 2Y8L which surround elongated rectangular areas in the X-axis direction, respectively, and extraction line portions 2Y1E, 2Y2E, . . . , 2Y8E which are continuously connected to the loop portions 2Y1L, 2Y2L, . . . , 2Y8L, respectively.
Also, the eight X-axis direction loop coils 2Y1 to 2Y8 are disposed in such a way that the loop portions thereof 2Y1L to 2Y8L are arranged in the Y-axis direction, and are formed in such a way that the extraction line portions thereof 2Y1E to 2Y8E extend in the Y-axis direction from the loop portions 2Y1L to 2Y8L, respectively. Also, each of the extraction line portions 2Y1E to 2Y8E is suitably bent at a right angle in the Y-axis direction and is bent in the Y-axis direction again so as to be connected to the connector portion 4.
It is noted that each of the extraction line portions 1X1E to 1X12E and the extraction line portions 2Y1E to 2Y8E is composed of two lines: a going line through which a signal is supplied or a signal is taken out; and a returning line which, for example, is connected to a reference electric potential, for example, a grounding electric potential.
In the sensor 100A in this example shown in FIG. 9, an area which is occupied by both of the loop portions 1X1L to 1X12L of the 12 X-axis direction loop coils 1X1 to 1X12, and the loop portions 2Y1L to 2Y8L of the eight Y-axis direction loop coils 2Y1 to 2Y8 becomes a position detection area 5 of a position indicated by the position indicator.
As shown in FIG. 9, the sensor 100A requires a large area which is occupied by both of the extraction line portions X1E to X12E and the extraction line portions Y1E to Y8E in the outside of the position detection area 5, which results in that a ratio of the dimension of the position detection area 5 to a total dimension of the substrate 3 becomes small. For this reason, for example, when the substrate 3 is accommodated in a chassis of an electronic apparatus in order to be used as a coordinate input device, there is caused a problem that a dimension of a coordinate input area becomes smaller than a dimension of the entire chassis.
In light of this problem, the patent applicant has previously provided an invention as described in Patent Document 1 of Japanese Patent No. 2842717 (official gazette), wherein on one sheet of substrate, an extraction line portion was formed within a position detection area and was also formed in a planar surface different from that of a loop portion, whereby a dimension of an area required for the extraction line portion is made small in the outside of the position detection area of a sensor.
FIG. 10 is a top plan view showing an example of a conductor pattern in a sensor 100B proposed in Patent Document 1 mentioned above. In the sensor 100B of this example shown in FIG. 10, a loop coil group 11 in the X-axis direction is formed on one surface of a substrate 13 having both of a front surface and a back surface, and a loop coil group 12 in the Y-axis direction is formed on a surface opposite to the one surface of the substrate 13.
The loop coil group 12 in the Y-axis direction is structured in the same manner as that in the loop coil group 2 in the Y-axis direction in the sensor 100A of the example shown in FIG. 9. However, in the loop coil group 11 in the X-axis direction, a structure of the extraction line portion thereof is different from the loop coil group 1 in the X-axis direction in the sensor 100A of the example shown in FIG. 9.
That is to say, as shown in FIG. 10, loop portions 11X1L to 11X12L of 12 X-axis direction loop coils 11X1 to 11X12 of the loop coil group 11 in the X-axis direction are formed on one surface of the substrate 13. On the other hand, extraction line portions 11X1E to 11X12E of the 12 X-axis direction loop coils 11X1 to 11X12 are formed within an area corresponding to a position detection area 15 on the other surface side of the substrate 13. In this case, the extension line portions 11X1E to 11X12E of the 12 X-axis direction loop coils 11X1 to 11X12 on the other surface side of the substrate 13 are connected to the loop portions 11X1L to 11X12L on one surface side of the substrate 13 via through holes (not shown), respectively.
As a result, since the extraction line portions 11X1E to 11X12E of the 12 X-axis direction loop coils 11X1 to 11X12 of the loop coil group 11 in the X-axis direction can be formed within the position direction area 15, a length of the substrate 13 in the Y-axis direction can be made shorter than that of the sensor 100A. For this reason, a circumferential portion of the position direction area 15 of the substrate 13 can be reduced in size.